Dislocation Nucleation Process Research Articles

An MBE growth facility for real-time in situ synchrotron x-ray topography studies of strained-layer III–V epitaxial materials

This paper describes a unique combined UHV MBE growth x-ray topography facility designed to allow the first real-time synchrotron radiation x-ray topography study of strained-layer III–V growth processes. This system will enable unambiguous determination of dislocation nucleation and multiplication processes as a function of controlled variations in growth conditions, and also during post-growth thermal processing. The planned experiments have placed very stringent demands upon the engineering design of the system, and design details regarding the growth chamber; sample manipulator, x-ray optics, and real-time imaging systems are described. Results obtained during a feasibility study are also presented.

Dislocation nucleation near the critical thickness in GeSi/Si strained layers

Abstract A theoretical and experimental study is presented of dislocation nucleation processes in the initial stages of coherency breakdown in GeSi/Si(100) strained layers. It is shown that the use of dislocation core parameters appropriate to semiconductors leads to far higher predictions than in previous studies for the activation energy for half-loop nucleation. Homogeneous nucleation is thus unlikely at low misfit in the absence of stress concentrations at large surface steps. Experimentally the actual nucleation processes in GeSi epilayers at low (less than 1%) misfit are deduced from the microstructure at the earliest stages of dislocation introduction. The first dislocations are shown to be 60[ddot] (a/2) half-loops on the inclined [111] planes. Detailed investigation shows that these can be attributed to the operation of a completely new type of (heterogeneous) regenerative nucleation source. This involves the dissociation of a pre-existing (a/6) stacking fault (the ‘diamond defect’) to ...

Experimental and Theoretical Analysis of Strain Relaxation in GexSi1-x/Si(100) Heteroepitaxy

ABSTRACTBy analyzing in-situ strain relaxation measurements of GexSi1-x/Si(100) epitaxy in a Transmission Electron Microscope, we are able to quantify the fundamental parameters which describe strain energy relaxation via misfit dislocation introduction. Quantitative descriptions of misfit dislocation nucleation, propagation and interaction processes are derived. The numerical parameters obtained from these experiments are then incorporated into a predictive theoretical model of strain relaxation whichrelies only upon experimentally measured quantities. Good agreement between experiment and theory is obtained over a wide range of data.

Dislocation Nucleation Models From Point Defect Condensations in Silicon and Germanium

ABSTRACTThe process of dislocation nucleation from point defect condensations in Si(Ge) is discussed. Based on the assumption that during the dislocation nucleation stage, the dominant factor in the configurational energy is the number of dangling bonds per point defect incorporated, rather than the more commonly recognized factor of strain energy, it is possible to model the dislocation nucleation process. In order to minimize the number of dangling bonds, point defects would condense into row configurations elongated in <110>, called intermediate defects (IDC), and then the IDCs would evolute into undissociated 90° edge –, 60°, and Frank partial dislocations.

The Compressive Deformation Behavior of Long Range Ordered Polycrystalline iron—aluminum Alloys

AbstractThe compressive deformation behavior of polycrystalline iron‐aluminum alloys has been investigated (i) at 298°K for specimens heat treated in various ways and containing from 22.0 to 31.7 at% Al, and (ii) from 77 to 655°K for well‐annealed specimens containing 26.6 at% Al. Alloys which possess significant DO3 type long range order exhibit marked composition and temperature dependent variations in deformation behavior. Specifically, those containing ⪆ 27 at% Al exhibit two linear and one parabolic deformation stage at 298°K. The linear stages are shown to be a result of the production and motion of DO3 type superlattice dislocations. The absence of these stages in well‐annealed specimens is attributed to the lack of thermal assistance for the DO3 superlattice dislocation nucleation process. The flow stress levels which characterize the two linear stage behavior agree with calculations of the stress required for production of antiphase boundaries. Results obtained from quenched specimens are in agreement with the above conclusions, and the changes induced by quenching are in accord with calculations of the effect of thermal antiphase boundaries upon dislocation motion.